问题

RT

算法：模拟

经典题。关在在于模拟四个方向、确定方向变换的条件（走到不能走了）、遍历的终点（从0到m*n)

复杂度

时间：O(NM)
空间：O(NM)

代码

class Solution {
public:
    vector<int> spiralOrder(vector<vector<int>>& matrix) {
        int i = 0, j = 0;
        int m = matrix.size();
        if(!m) return {};
        int n = matrix[0].size();
        vector<int> ans;
        int d = 1;
        int dx[4] = {-1, 0, 1, 0}, dy[4] = {0, 1, 0, -1};
        vector<vector<bool>> vis(m, vector<bool>(n));
        for(int k = 0; k < m*n; k ++){
            vis[i][j] = true;
            ans.push_back(matrix[i][j]);
            int x = i + dx[d], y = j + dy[d];
            if(x < 0 || x >= m || y < 0 || y >= n || vis[x][y]){
                d = (d+1)%4;
                x = i + dx[d], y = j+dy[d];
            }
            i = x, j = y;
        }
        return ans;
    }
};